No MIT license file in the repository

[matthewcarbone]

This is essentially a repeat of #15 but I'm making a new issue for visibility. It's noted that the license is MIT in the README, but there is no MIT license in the repository. This might make the usage of the code here a bit ambiguous. @karpathy, would you mind adding the actual LICENSE file to remove any ambiguity?

I'll also take a moment to note that this is bar none the best tutorial on transformers and LLM usage I have ever seen, hence why I want to use some of it for my students/interns. But I'm hesitant to do so until the license is updated. Thanks!